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United States Patent |
5,179,213
|
Bradshaw
,   et al.
|
January 12, 1993
|
Macrocyclic ligands bonded to an inorganic support matrix and a process
for selectively and quantitatively removing and concentrating ions
present at low concentrations from mixtures thereof with other ions
Abstract
A process of separating one or more seleced species of ions from a solution
containing the ions comprises contacting the solution with a novel
composition of matter comprising a hydrocarbon chain covalently bonded to
a macrocyclic compound, wherein the macrocyclic compound has at least four
--A--C--C-- linkages in which A for each such linkage, is independently
selected from the group consisting of O, O--CH.sub.2, S, SH.sub.2, NR, and
NRCH.sub.2, with R being independently selected from the group consisting
of hydrogen, alkyl and benzyl, and wherein the hydrocarbon chain has an
end group
##STR1##
with X being independently selected from the group consisting of lower
alkyl, benzyl, phenyl, halogen, O--CH.sub.3, O--C.sub.2 H.sub.5 and
O-matrix, and with matrix being independently selected from the group
consisting of silica, silica gel, glass, glass fibers, titania, zirconia,
alumina and nickle oxide. A complex is formed between the selected ions
and the composition of matter to remove the selected species of ions from
the solution. The solution is separated from the complex, and the complex
is thereafter contacted with an eluant which frees the selected ions from
the complex into solution in the eluant.
Inventors:
|
Bradshaw; Jerald S. (Provo, UT);
Izatt; Reed M. (Provo, UT);
Christensen; Virginia B. (Provo, UT);
Bruening; Ronald L. (Provo, UT)
|
Assignee:
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Brigham Young University (Provo, UT)
|
Appl. No.:
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517127 |
Filed:
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May 1, 1990 |
Current U.S. Class: |
549/3; 549/4; 549/10; 549/11; 549/210; 549/214; 549/347 |
Intern'l Class: |
C07D 327/00; C07D 325/00 |
Field of Search: |
549/3,4,10,11,210,214,342
|
References Cited
Other References
N. Nakajima et al., Journal of Liquid Chromatography, 7 (11), pp. 2115-2125
(1984).
M. Lauth et al., Journal of Liquid Chromatography, 8 (13), pp. 2403-2415
(1985).
R. M. Izatt et al., Chem. Rev., "Thermodynamic and Kinetic Data for
Cation-Macrocycle Interaction", 85, 271-339 (1985).
L. F. Lindoy, "Progress in Macrocycle Chemistry", ed R. M. Izatt et al.,
pp. 53-92, John Wiley & Sons, New York (1987).
V. Dudler, et al., Aust. J. Chem., "An Oxygen-Nitrogen Donor Macrocycle
Immobolized on Silica Gel", 40, pp. 1557-1563 (1987).
S. L. Regen, Angew. Chem. Int. Ed. Eng., "Triphase Catalysts", 18, (6), pp.
421-492 (1979).
|
Primary Examiner: Raymond; Richard L.
Assistant Examiner: Russell; M. W.
Attorney, Agent or Firm: Thorpe, North & Western
Parent Case Text
INTRODUCTION
This application is a continuation-in-part of our copending application
Ser. No. 07/240,689 filed Sep. 06, 1988 now U.S. Pat. No. 4,943,375.
Claims
We claim:
1. A composition of matter represented by the structural formula:
##STR7##
in which A is a member selected from the group consisting of O,
O--CH.sub.2, S and S--CH.sub.2 ; I is a member selected from the group
consisting alkyl, alkoxy, chlorine and O-matrix; Y is selected from the
group consisting of O and CH.sub.2 ; a is an integer of from 2 to 16 and n
is an integer of from 0-2 and matrix is a member selected from the group
consisting of silica, silica gel, glass, glass fibers, titania, zirconia,
alumina and nickel oxide.
2. A composition according to claim 1 wherein matrix is selected from the
group consisting of silica and silica gel.
3. A composition according to claim 2 wherein Y is 0, n is 3 and X is a
member selected from the group consisting of methyl, alkoxy, chlorine and
O-matrix.
4. A composition according to claim 3 wherein A is 0.
5. A composition according to claim 3 wherein A is S.
6. A composition according to claim 4 wherein matrix is silica.
7. A composition according to claim 4 wherein matrix is silica gel.
Description
The present invention comprises novel compositions of matter and processes
of using them. The compositions of matter comprise an inorganic solid
support matrix, e.g., silica, silica gel, glass, glass fibers, titania,
zirconia, alumina and nickel oxide, which is covalently bonded to a
hydrocarbon chain which in turn is bonded to a macrocyclic ligand either
directly or through an ether oxygen linkage. The macrocyclic ligand is
selected from compounds which have at least four --A--CH.sub.2 --CH.sub.2
-- groups in which A is independently selected from O, O--CH.sub.2, S,
S--CH.sub.2, NR, and NRCH.sub.2, with R being independently selected from
H, lower alkyl and benzyl. The hydrocarbon chain has an end group
consisting of
##STR2##
covalently bonded thereto, wherein X is selected from lower alkyl, phenyl,
benzyl, halogen, O--CH.sub.3, OC.sub.2 H.sub.5, and O-matrix.
Representative families of compounds, i.e., complexing agents, contemplated
by the present invention are illustrated by the following structural
formulae I to V.
##STR3##
wherein A is defined as above X is selected from the group consisting of
alkyl, alkoxy, chlorine and O-matrix; Y is selected from the group
consisting of O and CH.sub.2 ; R' is selected from the group consisting of
hydrogen and alkyl; R'' is selected from the group consisting of hydrogen,
lower alkyl and aryl; a is an integer from 2 to 16; m, n and p are
integers from 0 to 2.
The process comprises selectively and quantitatively removing and
concentrating one or more selected species of ions present at low
concentrations from a plurality of other ions in a multiple ion solution
in which the other ions may be present at much higher concentrations. The
multiple ion solution is brought into contact with a composition of matter
of the invention. The preferred embodiment disclosed herein involves
carrying out the process by bringing a large volume of the multiple ion
solution into contact with a complexing agent consisting of a macrocyclic
ligand covalently bonded through a hydrocarbon side chain to a solid
inorganic support matrix. Contact is preferably made in a separation
column containing the complexing agent. The multiple ion solution passes
through the column to complex the desired ion or ions with the complexing
agent. Following the complexing step, a small volume of a receiving liquid
or eluant is brought into contact with the loaded complexing agent to
break the complex by chemical or thermal means and to dissolve the desired
ions and carry them away from the complexing agent. Various contact
apparatus may be used instead of a column. The multiple ion solution can
be slurried or mixed with the complexing agent in a stirred vessel vessel,
for example. The loaded complexing agent is then separated from the
solution and washed with a receiving liquid or eluant to break the complex
and recover the desired ion or ions from the complexing agent. The desired
ions can then be recovered from the receiving phase by well known
procedures.
More particularly, the process comprises forming a chemical covalent bond
between an inorganic solid support member, such as those mentioned
previously including silica and silica gel, and at least one of the
macrocyclic ligands to from the complexing agent. The complexing agent is
then introduced into a contacting device such as a tall column. The
solution containing the multiple species of ions flows through the column
in contact with the complexing agent, whereby the desired ions complex
with the complexing agent. The desired ions are thus separated from the
rest of the mixture which flows out of the column. A small volume of the
receiving liquid or eluant is then passed through the column to break the
complex and dissolve and carry out of the column the device ion(s). The
desired ions are then recovered from the receiving phase by well known
procedures.
BACKGROUND OF THE INVENTION
The fact is known that macrocyclic polyethers and other macrocyclic ligands
present as solutes in a solvent such as water are characterized by their
ability to selectively form strong bonds with particular ions or groups or
ions present as solutes in the same solvent according to size, donor
atom-related and other well known selectivity rules as noted in articles
by R. M. Izatt, J. S. Bradshaw, S. A. Nielsen, J. D. Lamb, J. J.
Christensen, and D. Sen, THERMODYNAMIC AND KINETIC DATA FOR
CATION-MACROCYCLE INTERNATIONAL, Chem. Rev., 1985, Vol. 85, 271-339 and by
L. F. Lindoy, in PROGRESS IN MACROCYCLIC CHEMISTRY, edited by R. M. Izatt
and J. J. Christensen, JOHN WILEY & SONS, pages 53-92 (1987). However,
researchers have not previously been able to incorporate macrocycles into
separation systems where the behavior of the macrocycle in the separation
system in comparison to that of the macrocycle as a solute is unchanged
and/or the macrocycle will remain in the separation system. Articles such
as those entitled ION-CHROMATOGRAPHIC SEPARATION OF SILICA GRAFTED WITH
BENZO-18-CROWN-6-ETHER by M. Lauthard and Ph. Germain, J. Liquid
Chromatogr., 1985, Vol. 8, 2403-2415, and ION-CHROMATOGRAPHY ON POLY
(CROWN ETHER-MODIFIED) SILICA POSSESSING HIGH AFFINITY FOR SODIUM by M.
Nakajima, K. Kumura, E. Hayata and T. Shono, J. Liquid Chromatogr., 1984,
Vol. 7, 2115-2125have disclosed the bonding of crown ethers to silica gels
but they and most other reported macrocycle bonded silicas contain a
benzene group or other electron withdrawing groups as part of a macrocycle
side chain which reduces the ability of the macrocycle to bond with ions
in comparison to the situation where the macrocycle and ions are present
as solutes in solution. The only other reported examples of bonding of
macrocycles to sand or silica gel have involved bonding via a side chain
connected to one of the electron rich macrocycle donor atoms, i.e.,
nitrogen. One such reference is entitled AN OXYGEN-NITROGEN DONOR
MACROCYCLE IMMOBILIZED ON SILICA GEL. A REAGENT SHOWING HIGH SELECTIVELY
FOR Cu (II) IN THE PRESENCE OF Co(II), Ni(II) OR Zn(II), by V. Dudler, L.
F. Lindoy, D. Sallin, C. W. Schlaepfer, Aust. J. Chem., 1987, Vol. 40, p.
1557. However, such bonding changes the geometry of the compound and
greatly reduces the ability of the macrocycle to interact with ions. Prior
researchers in this field confined their research to analytical
chromatographic applications and disclosed no concept of industrial
separation applications where strong macrocycle-ion bonding is required to
quantitatively recover the desired ion(s) from solution and high
selectivity is required to obtain a product free from contaminants. The
strength of macrocycle-ion bonding is particularly important when ions
present in solution at low concentrations need to be recovered. The
greater the value of the equilibrium constant for ion-macrocycle
interaction, the lower the initial concentration of the ion in solution
can be and still be efficiently and quantitatively complexed. Hence, the
ability to attach these macrocycles to an inorganic, solid support, such
as sand or silica gel, without reducing the ability of the macrocycle to
complex ions is of the utmost importance in the industrial use of
macrocycles. The process of the present invention successfully
accomplished this feat.
SUMMARY OF THE INVENTION
The compounds of the present invention comprise certain macrocyclic ligands
covalently bonded to a solid inorganic support matrix, such as those
mentioned previously including silica and silica gel. The compounds so
produced are identified above. The process of the present invention uses
the novel compounds to selectively separate and recover desired species of
ions from solutions containing multiple species of ions. The complexing
agents of the present invention are characterized by high selectivity for
and removal of desired metal ions or groups of metal ions from a solution
containing multiple species of ions, even when species of undesired ions
are present in much higher concentrations than the desired species of
ions. The process of selectively removing and concentrating the desired
ion(s) is characterized by the ability to quantitatively complex from a
large volume of solution the desired ion(s) when they are present even at
very low concentrations. The desired ions are recovered from the
separation column by flowing a small volume of a receiving phase or eluant
through the column. The eluant contains a solubilized reagent which need
not be selective, but which will strip the ions from the macrocyclic
ligand quantitatively. The recovery of the desired metal ions from the
receiving phase or eluant is easily accomplished by well known procedures.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described and illustrated by reference to the
drawings in which:
FIG. 1 represents schematically a suitable column which contains the novel
macrocyclic ligand materials of the present invention and through which a
solution of desired ions can flow in contact with the ligand materials to
selectively form a complex between the desired ion or group of ions in
accordance with the invention.
FIG. 2 represents a graph of the predicted (o points) and actual (curve)
remaining amount of Sr.sup.2+ in a solution initially containing 1 M
MgCl.sub.2 and 0.001 M SrCl.sub.2 after flowing the solution through a
column containing an 18-crown-6 bonded silica gel vs. the amount of volume
of the solution which has been passed through the column. The analytical
detection limit is shown by small triangles for those experimental points
where no Sr.sup.2+ could be detected.
DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
PREPARATION OF MATERIALS
Macrocycles which do not contain electron withdrawing groups and which are
capable of being bonded to the solid inorganic matrix, such as silica,
silica gel, glass, glass fibers, titania, zirconia, alumina and nickel
oxide, are synthesized. Then the macrocycle is covalently bonded to the
inorganic support matrix. One method of preparing the compounds of Formula
I, for example, is to react the allyloxy forms of the crowns with
triethoxysilane (or trichlorosilane or dichloromethylsilane or
chlorodimethylsilane) followed by heating the resulting silane with silica
as follows:
##STR4##
The synthesis of the allyloxy forms of the crowns, which is not part of the
present invention, is described in an article entitled FACILE SYNTHESIS OF
HYDROXYMETHYLCROWN ETHERS by I. Ikeda, H. E. Mura and M. Okahara,
Synthesis pages 73 and 74 (1984), which is incorporated herein by
reference.
A method for preparing the macrocyclic compounds of Formula II is to react
the cryptand compound having a --CH.sub.2 --O--CH.sub.2 CH.dbd.CH.sub.2
side chain with triethoxysilane (or trichlorosilane or
dichloromethylsilane or chlorodimethylsilane) in the presence of a
platinum catalyst to convert the side chain to --CH.sub.2
--O--(CH.sub.2).sub.3 --Si(CH.sub.3)ClX (where X=(Cl or CH.sub.3) and
heating this compound with silica as follows:
##STR5##
The synthesis of the --CH.sub.2 --O--CH.sub.2 CH.dbd.CH.sub.2 substituted
2.2.2 cyrptand (p=n=m=1) which is not part of the present invention, is
described in an article entitled SYNTHESIS OF HYDROXYMETHYL-FUNCTIONALIZED
DIAZACROWNS AND CRYUPTANDS by David A. Babb, Bronislaw P. Czech and
Richard A. Bartsch, J. Heterocyclic Chem., Vol. 23, pages 609, 613 (1986),
which is incorporated herein by reference.
A method of preparing the macrocyclic compounds of Formula III, for
example, is to react 4-allyloxypyridino-18-crown-6 with triethoxysilane
(or trichlorosilane or dichloromethylsilane or chlorodimethylsilane) and
heating the resulting chlorosilane and silica as follows:
##STR6##
The synthesis of 4-allyloxypyridino-18-crown-6 (where n =1), which is not
part of the present invention, is described in an article entitled
PROTON-IONIZABLE CROWN ETHERS. 3. SYNTHESIS AND STRUCTURAL STUDIES OF
MACROCYCLIC POLYETHER LIGANDS CONTAINING A 4-PYRIDONE SUBCYCLIC UNIT, by
Jerald S. Bradshaw, Yohji Nakatsuji, Peter Huszthy, Bruce E. Wilson, N.
Kent Dalley and Reed M. Izatt, J. Heterocyclic Chem. Vol. 23, pages
353-360 (1986), which is incorporated herein by reference.
It should be emphasized that any macrocycle which can by synthesized with a
--CH.sub.2 --O--CH.sub.2 CH.dbd.CH.sub.2 side chain or the like attached
to one of the regular carbon atoms of the macrocycle could then be
covalently bonded to the solid support matrix, such as silica or silica
gel. The interaction properties of this bonded macrocycle will not differ
from those of the unsubstituted macrocycle present as a solute in solution
when such a macrocycle does not contain electron withdrawing substituent
groups and the bonding to sand or silica gel does not occur via one of the
macrocycle donor atoms. This will now be described in more detail in the
following description of the metal ion recovery and concentration process.
METAL ION RECOVERY AND CONCENTRATION
The metal ion recovery and concentration process of the invention relates
to the selective recovery of desired metal ions from mixtures thereof with
other metal ions using the compounds of the invention as defined above.
Effective methods of recovery and/or separation of metal ions,
particularly silver, lead, cadmium, and other heavy metals, from one
another in culinary water supplies, waste solutions, deposits and
industrial solutions and silver recovery from waste solutions, e.g., from
emulsions on photographic and Xray film, represent a real need in modern
technology. These ions are typically present at low concentrations in
solutions containing other ions at much greater concentrations. Hence,
there is a real need for a process to selectively recover and concentrate
these hazardous and/or desirable ions. The present invention accomplishes
this separation effectively and efficiently by the use of the macrocyclic
ligands bonded to the solid support matrix in accordance with the present
invention.
The process will be described with respect to macrocyclic ligands bonded to
silica, such as the compounds shown in Formulas I through V. A
macrocycle-bonded silica compound is chosen that will selectively complex
the ion(s) of interest. There is a large data base for measurements of
macrocycle-ion interactions where the macrocycle is unsubstituted and
present as a solute in a solvent. Much of this data base is presented in
an article by R. M. Izatt, J. S. Bradshaw, S. A. Nielsen, J. D. Lamb, J.
J. Christensen, and D. Sen, THERMODYNAMIC AND KINETIC DATA FOR
CATION-MACROCYCLE INTERACTION, Chem. Rev. Vol. 23, 271-339 (1985).
Previously, this data base has only provided general qualitative
predictions about the behavior of macrocycles incorporated into separation
processes. However, in the process of the invention the equilibrium
constants for ion-macrocycle interaction for macrocycles present as
solutes in solution vs. that for macrocycles bonded to silica show little
or no variation. Data comparing the interaction of several ions with both
types of the macrocycle 18-crown-6 are given as an example of this point
in Table 1.
TABLE 1
______________________________________
Comparison of Aqueous Equilibrium Constants for 1:1
Cation-18-Crown-6 Interaction with the Macrocycle Free
in Solution vs. being Bound to Silica Gel
Log K*
Free Bound
Cation Macrocycle
Macrocycle
______________________________________
Sr.sup.2+ 2.72 2.6*
Tl.sup.+ 2.27 2.2**
Ba.sup.2+ 3.87 3.7**
Pb.sup.2+ 4.27 4.0***
Ni.sup.2+ 0 0.2**
______________________________________
*Log K values for the free marocycle, which are not part of the present
invention, are taken from R. M. Izatt, J. S. Bradshaw, S. A. Nielsen, J.
D. Lamb, J. J. Christensen, and D. Sen, THERMODYNAMIC AND KINETIC DATA FO
CATIONMACROCYCLE INTERACTION, Chem. Rev., Vol. 85, 271-339 (1985). Log K
values for the bound macrocycle were determined by us.
**Ionic strength = 3 M.
***Ionic strength = 1 M.
It is emphasized that similar interaction with metal ions of the bonded
macrocycle and macrocycle in solution is only obtained when electron
withdrawing groups are not attached to the macrocycle and when the
macrocycle is not attached to the silica via one of the donor atoms of the
macrocycle.
The data base for macrocycle-cation interaction can be used in choosing a
macrocycle for recovering a particular cation. The selective removal and
recovery of Pb.sup.2+ and Ba.sup.2+ from aqueous solutions using
18-crown-6 bonded to silica gel are examples of a suitable choice of
macrocycle for a specific need. The data base measurements indicate that
Pb.sup.2+ and Ba.sup.2+ are selectively complexed by 18-crown-6 by at
least an order of magnitude over all other cations. The selectivity over
cations often present in large excess (i.e., Na.sup.+, K.sup.+, Mg.sup.2+,
Ca.sup.2+) is much greater. The equilibrium constant values in Table 1
confirm the suitability of the choice of 18-crown-6 as an appropriate
macrocycle for the task. The 18-crown-6 bonded silica gel complexing agent
has been tested for its ability to remove Pb.sup.2+ from H.sub.2 O. These
data are presented in Table 2. The diameter of the cylindrical used in
developing the data reported in Table 2 was 1.9 cm, and the amount of
complexing agent was sufficient to fill a 3.5 cm section of the column.
The complexing agent comprised 5.3 moles of macrocycle per cubic meter of
silica gel. The detection limit of the atomic absorption spectrophotometer
used was 30 ppb (parts per billion).
TABLE 2
______________________________________
The Reduction of Pb.sup.2+ Concentrations in Aqueous
Solution Using an 18-Crown-6 Bonded Silica Gel Column
Initial Pb.sup.2+
Final Pb.sup.2+
Volume of Pb.sup.2+
Concentration
Concentration
Solution
(ppm) (ppb) (ml)
______________________________________
207* <30 50
10** <30 >250
20*** <30 100
______________________________________
*Mg.sup.2+ was also present at a concentration of 1 Molar.
**Mg.sup.2+ and Ca.sup.2+ were also present at 0.6 and 0.003 Molar,
respectively.
***Mg.sup.2+ was also present at 0.7 Molar.
The data in Table 2 show that great reductions in aqueous Pb.sup.2+
concentrations can be achieved using the 18-crown-6 bonded silica gel
column even when another cation is present in solution at much greater
concentrations. Silica gel can interact with ions to some degree in and of
itself. However, tests using a plain silica gel column under conditions
identical to those performed with the macrocycle bonded silica gel showed
that the aqueous stream Pb.sup.2+ concentration reductions were not as
great. In particular, the plain silica gel column performed quite poorly
under conditions where cations other than Pb.sup.2+ were present at much
greater concentrations than that of Pb.sup.2+. The effect of silica gel or
sand interaction with ions flowing through the column can be minimized by
blocking the majority of the --OH sites present with trimethylsilyl
groups.
The same 18-crown-6 bonded silica gel column has also been tested for its
ability to selectively remove Sr.sup.2+ from a solution containing 1 M
MgCl.sub.2 and 0.001 M SrCl.sub.2. The molar concentrations of Sr.sup.2+
in the aqueous stream coming out of the bottom of the column vs. the
corresponding volumes of solution which have been flowed through the
column are plotted as the exponential points in FIG. 2. A predicted
Sr.sup.2+ concentration vs. volume plot is also shown (solid line). The
predicted plot was obtained by numerically solving the partial
differential mass balance equation for the column using the equilibrium
constant for Sr.sup.2+ interaction. Similar tests with sand and silica
gel columns which did not contain the bonded macrocycle showed that very
little Sr.sup.2+ could be removed from the aqueous source phase.
Once the desired ion(s) are attached to the silica gel column they must be
removed using a small volume of a receiving phase so that a concentrated
and purified product is obtained. In the Pb.sup.2+ and Sr.sup.2+
recovery tests described, 99% of the purified Pb.sup.2+ or Sr.sup.2+ was
recovered from the column using 25 ml of a concentrated basic solution of
either ethylenediamine tetraacetic acid (EDTA), citrate or acetate. These
reagents form stronger complexes with the ion(s) that the macrocycle does.
Hence, they can effectively strip ion(s) from the macrocycle. These
ion-receiving phase reagent complexes are easily broken by adding acid to
the solution. These species can be recovered as a solid if desired. For
example, the Pb.sup.2+ can be recovered as a solid by using H.sub.2
SO.sub.4 as the acid and, hence, precipitating PbSO.sub.4.
An example of the use of these materials and processes is the quantitative
and selective removal of undesired heavy metals such as Pb.sup.2+ from
blood. The silica-gel bonded macrocycle 18-crown-6 (FIG. 2. A-F=oxygen,
n=1) selectively complexes Pb.sup.2+ over K.sup.+, Na.sup.+, Ca.sup.2+,
Fe.sup.3+, proteins and other materials necessary in the body by at least
2 orders of magnitude.
Although the invention has been described and illustrated by reference to
certain specific macrocyclic ligands and processes of using them, analogs
of these macrocycles are within the scope of the compounds and processes
of the invention as defined in the following claims.
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